1. Field of the Invention
The present invention relates to a pickup device for an acoustic stringed instrument typified by a guitar, a ukulele, a mandolin, a violin, a cello, a contrabass, a banjo, or a samisen, and more specifically, to a sound processing method and a pickup device vibration sensor for a stringed instrument which convert the vibration force of the stringed instrument into electric signals for output.
2. Description of the Related Art
Naturally, in particular, stringed instruments require an excellent pickup device which allows strings to exhibit well-balanced acoustic characteristics, which can provide favorable outputs, and which does not hinder the propagation of the vibration of the strings to the body, which is characteristic of acoustic stringed instruments.
For this purpose, to collect electrically sounds from an acoustic stringed instrument, a microphone attached to a stand was frequently used. However, the player's movement varied the distance between the microphone and the instrument or their positional relationship. This prevented sounds from being stably collected. Thus, this problem was solved by attaching the microphone to the musical instrument.
However, because of the use of the microphone, if the collected sound is amplified and outputted through a speaker in a concert hall, the sound may enter the microphone again which is attached to the instrument. In this case, the sound is fed back to cause an oscillation phenomenon called “howling”. This restricts the electric expansion of sounds from the instrument (refer to Japanese Patent Laid-Open No. 2002-236486 (Abstract)).
Furthermore, devices called “pickups” are commercially available which collect sounds by using a sensor to convert the vibration of a sound source in the instrument into electric signals. The pickup device sharply reduces the ratio of external sounds to sounds from the instrument on which the pickup device is mounted. It is thus possible to reduce the magnitude of the feedback that may occur when instrument sounds are electrically expanded. The pickup device is therefore very useful in electrically expanding instrument sounds but has the problems described below.
By way of example, description will be given of a conventional technique applied to an acoustic guitar. A pickup device for such an acoustic guitar captures and converts the vibration of each string into electric signals by arranging a sensor between a saddle and a bridge which transmit the vibration of each string to a top plate. In this case, the sensor is located too close to the strings. It is thus difficult to pick up the vibration of the top plate, which is characteristic of the tone of the acoustic guitar. Consequently, many of the components of the vibration of the strings are converted into electric signals to prevent the reproduction of the attractive characteristic tone of the acoustic guitar. Furthermore, when the sensor is mounted, an expert in musical instruments must be asked to process and adjust the instrument carefully. Therefore, mounting the sensor is difficult.
Furthermore, a type of a conventional pickup device (refer to National Publication of International Patent Application No. 2002-515258 (Abstract)) is stuck to the top plate using a pressure sensitive adhesive coated tape or an adhesive. With this pickup device, picked-up sounds have certain peculiarities and the tone is thus inappropriate because the top plate has complicated vibration characteristics. Furthermore, when such a stuck type pickup device is removed, varnish may disadvantageously be released from the top plate.
Another conventional pickup device secures a piezoelectric transducer to a belly of a stringed instrument using a C-shaped clamp. The clamp in this instrument pickup assembly is attached to the exterior and the back surface of the top, vibrating belly of the instrument, near a soundhole. Thus, the transducer vibrates along with the top, vibrating plate, and it acts to pick up the corresponding vibration accelerations. This device, again, poses the problem of picking up the complicated vibration characteristics and peculiarities associated with the top plate (refer to U.S. Pat. No. 6,274,801 B1).
Thus, although pickup devices of various structures have been provided for acoustic stringed instruments, sounds reproduced by these pickup devices cannot sufficiently reproduce the attractive tone of the acoustic stringed instrument.
Furthermore, another type of a conventional acoustic guitar pickup device has a sound hole formed in the top plate and in which an electromagnetic pickup is mounted to capture and convert the vibration of the strings into electric signals.
However, this device picks up only the vibration of the strings and thus reproduces little of the attractive tone of the acoustic guitar. The tone obtained is like that of an electric guitar. Therefore, this device cannot provide the attractive tone of the acoustic guitar (refer to Japanese Patent Laid-Open No. 7-5883 (Abstract)).
Yet another example of an electromagnetic pickup device, this time applied to either a drum or a guitar, attempts to control vibrations by converting vibration velocities at the vibrating surface to electrical signals. Such a device would typically aim to reduce the levels of electrical signal output, in order to achieve vibration control. Thus, again, the complicated vibration characteristics and peculiarities of the vibrating surface may result in inappropriate tones (refer to U.S. Pat. No. 3,725,561).